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Disorder in quantum critical superconductors

Nature Physics volume 10, pages 120125 (2014) | Download Citation

Abstract

In four classes of materials—the layered copper oxides, organics, iron pnictides and heavy-fermion compounds—an unconventional superconducting state emerges as a magnetic transition is tuned towards absolute zero temperature, that is, towards a magnetic quantum critical point1 (QCP). In most materials, the QCP is accessed by chemical substitution or applied pressure. CeCoIn5 is one of the few materials that are ‘born’ as a quantum critical superconductor2,3,4 and, therefore, offers the opportunity to explore the consequences of chemical disorder. Cadmium-doped crystals of CeCoIn5 are a particularly interesting case where Cd substitution induces long-range magnetic order5, as in Zn-doped copper oxides6,7. Applied pressure globally suppresses the Cd-induced magnetic order and restores bulk superconductivity. Here we show, however, that local magnetic correlations, whose spatial extent decreases with applied pressure, persist at the extrapolated QCP. The residual droplets of impurity-induced magnetic moments prevent the reappearance of conventional signatures of quantum criticality, but induce a heterogeneous electronic state. These discoveries show that spin droplets can be a source of electronic heterogeneity and emphasize the need for caution when interpreting the effects of tuning a correlated system by chemical substitution.

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Acknowledgements

We thank F. Ronning, M. Vojta and J. Shim for helpful discussions. Work at Los Alamos was performed under the auspices of the US Department of Energy, Office of Science, Division of Materials Science and Engineering and supported in part by the Los Alamos LDRD program. Work at SKKU is supported by an NRF grant funded by the Korean Ministry of Education, Science & Technology (MEST) (No. 2012R1A3A2048816 & 220-2011-1-C00014). R.R.U. acknowledges FAPESP (No. 2012/05903-6). V.A.S. acknowledges support by RFBR Grant 12-02-00376. X.L. acknowledges NSFC (No. 11374257).

Author information

Author notes

    • S. Seo
    •  & Xin Lu

    These authors contributed equally to this work

Affiliations

  1. Department of Physics, Sungkyunkwan University, Suwon 440-746, South Korea

    • S. Seo
    •  & Tuson Park
  2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    • Xin Lu
    • , J-X. Zhu
    • , R. R. Urbano
    • , E. D. Bauer
    • , V. A. Sidorov
    •  & J. D. Thompson
  3. Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310027, China

    • Xin Lu
  4. Instituto de Fisica ‘Gleb Wataghin’, Universidade Estadual de Campinas-SP, 13083-859, Brazil

    • R. R. Urbano
  5. Department of Physics, University of California, Davis, California 95616, USA

    • N. Curro
  6. Institute for High Pressure Physics, Russian Academy of Sciences, RU-142190 Troitsk, Moscow, Russia

    • V. A. Sidorov
  7. Department of Physics, University of California, Irvine, California 92697, USA

    • L. D. Pham
    •  & Z. Fisk

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Contributions

All authors discussed the results and commented on the manuscript. S.S. and X.L. performed the measurements and contributed equally to this work. R.R.U., V.A.S. and N.C. performed and analysed NQR experiments. E.D.B., L.D.P. and Z.F. provided samples, J-X.Z. performed theoretical calculations and T.P. and J.D.T. wrote the manuscript with input from all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Tuson Park or J. D. Thompson.

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DOI

https://doi.org/10.1038/nphys2820

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